| Affiliation: | 1. Institute for Groundwater Studies, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein 9300, South Africa;2. Department of Mathematics, Faculty of Sciences, Mehmet Akif Ersoy University, Burdur 15100, Turkey;1. Facultad de Matemáticas, Universidad Autónoma de Guerrero, Chilpancingo, Av. Lázaro Cárdenas S/N, Cd. Universitaria, Chilpancingo C.P. 39087, Guerrero, México;2. Escuela Superior de Medicina, Instituto Politécnico Nacional, Plan de San Luis y Díaz Mirón s/n, Col. Casco de Santo Tomas, Del. Miguel Hidalgo, Ciudad de México 11340, Mexico |
